This invention relates to tie members and more particularly to a tie member for mounting a transducer cable on a chain link fence or the like.
The fence protection system described in U.S. Pat. No. 3,763,482 utilizes a coaxial transducer cable as a line sensor connected to the fence fabric at longitudinally spaced points by fasteners or tie members. In addition to supporting the cable transducer, these tie members provide an efficient mechanical coupling between the fence and transducer so that intruder generated vibrations in the fence are transmitted to the cable which converts them into electrical signals detectable by signal processing circuits. The cable is readily installed by unskilled installers using conventional clamping tools.
The problem with this installation technique is that the coaxial cable is clamped directly against the fence fabric strands which are manufactured with varying degrees of roughness depending on the galvanizing process used. The burrs and rough spots on the strands often puncture or tear the outer covering of the cable, expose the interior to the elements and generally impair its capability to detect signals. In some instances in the field, such burrs have been found to have penetrated the cable sufficiently deeply to short the outer and inner conductors. On the other hand, if the cable transducer is not sufficiently tightly clamped to the fence, the efficiency of vibration coupling between fence and transducer is reduced and spurious signals may be generated by cable because of the play between the cable and fence.
In addition to damage from burrs, clamping of the cable with conventional tie members may result in excessive clamping forces being applied so as to cause indentation of the cable at the tie point. This tends to reduce the spacing between outer and inner conductors so as to impair cable sensitivity. The optimum clamping force for efficient operation of the transducer cable is not readily achieved with prior art tie members.
This invention is directed to an improved tie member which overcomes these problems.